cap off vs polish off

cap off and polish off both are verbs.

Word	Noun	Adjective	Verb	Adverb
cap off	No	No	Yes	No
polish off	No	No	Yes	No

As verbs, polish off is a hypernym of cap off; that is, polish off is a word with a broader meaning than cap off:

Other hypernyms of cap off include clear up, finish off, finish up, get through, mop up, wrap up.

cap off (verb)	polish off (verb)
finish or complete, as with some decisive action	finish a task completely
	finish eating all the food on one's plate or on the table
	kill intentionally and with premeditation